Interleaved winding for electrical inductive apparatus

ABSTRACT

Multiple-section interleaved winding having a plurality of coil disks, with each disk containing at least two coil sections. The disks are interconnected by a transposing type start-start connection and by a finish-finish connection. The number of turns in each disk and the location of the finish-finish connection are arranged to connect the outer turn of one coil section in a disk to the outer turn of a coil section in another disk, with the latter outer turn located radially within the outer turn of another coil section in the same disk. The turn and connection arrangements reduce the mutual coupling between disks when a surge voltage is applied to the winding.

Van Nice Aug. 12, 1975 INTERLEAVED WINDING FOR ELECTRICAL INDUCTIVE APPARATUS [75] Inventor: Robert I. Van Nice, Sharon, Pa.

[73] Assignee: Westinghouse Electric Corporation,

Pittsburgh, Pa.

[22] Filed: May 30, 1974 [21] Appl. No.: 474,851

[52] U.S. Cl. 336/70; 336/187 [51] Int. Cl. ..I-I01F 15/14 [58] Field of Search 336/69, 70, 186, 187; 174/34 [56] References Cited UNITED STATES PATENTS 3,493,907 2/1970 Stein et al 336/70 3,538,471 11/1970 Van Nice 336/70 3,781,739 12/1973 Meyer 336/70 FOREIGN PATENTS OR APPLICATIONS 646,174 9/1962 Italy 336/187 5A 148 6A 158 7A 763,479 12/1956 United Kingdom 336/187 Primary ExaminerThomas J. Kozma Attorney, Agent, or FirmJ. R. Hanway [5 7] ABSTRACT Multiple-section interleaved winding having a plurality of coil disks, with each disk containing at least two coil sections. The disks are interconnected by a transposing type start-start connection and by a finishfinish connection. The number of turns in each disk and the location of the finish-finish connection are arranged to connect the outer turn of one coil section in a disk to the outer turn of a coil section in another disk, with the latter outer turn located radially within the outer turn of another coil section in the same disk. The turn and connection arrangements reduce the mutual coupling between disks when a surge voltage is applied to the winding.

3 Claims, 10 Drawing Figures 4A 125 3A 118 2A 108 IA i 58 4A 125 3A 118 2A 108 IA 6A 7A 168 8A 175 9A iii INTERLEAVED WINDING FOR ELECTRICAL INDUCTIVE APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates, in general, to electrical inductive apparatus and, more specifically, to interleaved windings for power transformers.

2. Description of the Prior Art Interleaved windings are used in power transformers to reduce the voltage stresses within the winding when a surge voltage is applied thereto. One type of interleaved winding is described in U.S. Pat. No. 3,477,052 which is assigned to the assignee of this invention and which is incorporated herein by reference. A somewhat similar winding is described in U.S. Pat. No. 2,453,552. Although the winding structures described by these patents provide certain advantages over non-interleaved windings, some disadvantages of their use exist.

The winding described in U.S. Pat. No. 3,477,052 has a start-start connection arrangement which is more difficult to construct than the start-start connection arrangement described in U.S. Pat. No. 2,453,552. When a start-start connection connects winding turns located at the same radial position to each other, the conductors leaving the winding disks are often brought out together with one lying on top of the other. For relatively thick conductors, this produces an extra radial build in a limited region, which is undesirable. For the same reason, multiple strand versions of this type of winding have not been used considerably. The extra radial build can be reduced by separating the conductor crossover, that is, bringing each conductor out of the disk at a different circumferential position. However, this technique requires tough pieces of insulation on each side of the conductors to prevent shearing of the insulation wrapped around the conductors.

When the start-start connection connects together winding turns located at different radial positions, as described in U.S. Pat. No. 2,453,552, a natural form of conductor placement is developed which does not require heavy insulation or produce abrupt changes in the radial build of the winding structure. Thus, this type of start-start connection provides some mechanical advantages over the connection arrangement described in U.S. Pat. No. 3.477,052.

The surge voltage stress between the radial centers of the coil disks in a winding constructed according to U.S. Pat. No. 2,453,552 is not as good as that ofa winding constructed according to U.S. Pat. No. 3,477,052 for chopped wave and front-of-wave surges. Therefore, it is desirable, and it is an object of this invention, to provide an interleaved winding which provides the construction advantages of a winding constructed according to U.S. Pat. No. 2,453,552 and the electrical advantages of a winding constructed according to U.S. Pat. No. 3,477,052.

SUMMARY OF THE INVENTION There are disclosed herein new and useful arrangements for constructing an improved interleaved winding. In each of the various embodiments of the invention disclosed herein, the winding is wound with a plurality of conductors which spiral around a common axis to provide at least two coil sections which are formed by turns of the conductors. The coil sections of the disks are interconnected by startstart connections which connect together turns which are located at different radial positions. Finish-finish connections connect together the outermost turn of a coil section in one disk with the outermost turn of a coil section in an ad jacent disk. The turns are arranged, with an odd number of turns in at least one of the two disks, in a manner which connects the outermost turn of a coil section in one disk to the outermost turn of a coil section in the adjacent disk. A turn from another coil section in the adjacent disk is located radially outside of the turn to which the finish-finish connection is made. This provides, during a surge voltage condition, a conduction path for current flowing in the opposite direction than in the adjacent turn of the other coil section. The flux produced by the current distributions in the outer conductors during surge voltages are not in phase and reduce the mutual coupling between the disks.

BRIEF DESCRIPTION OF THE DRAWING Further advantages and uses of this invention will become more apparent when considered in view of the following detailed description and drawing, in which:

FIG. 1 is a schematic view of an interleaved winding constructed according to the prior art;

FIG. 2 is a spiral diagram of the winding shown in FIG. 1;

FIG. 3 is a schematic view of another interleaved winding constructed according to the prior art;

FIG. 4 is a spiral diagram of the winding shown in FIG. 3;

FIG. 5 is a schematic view of a single-strand interleaved winding constructed according to one embodiment of this invention;

FIG. 6 is a spiral diagram of the winding shown in FIG. 5;

FIG. 7 is a schematic view of a single-strand interleaved winding constructed according to another embodiment of this invention;

FIG. 8 is a spiral diagram of the winding shown in FIG. 7;

FIG. 9 is a schematic view of a multiple-strand interleaved winding constructed according to this invention; and,

FIG. 10 is a spiral diagram of the winding shown in FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Throughout the following description, similar refercharacters refer to similar elements or members in all of the Figures of the drawing.

Referring now to the drawing, and to FIG. 1 in particular, there is shown a portion of an interleaved winding 11 constructed according to the prior art, and more particularly according to the teachings of U.S. Pat. No. 2,453,552. The coil disks 10 and 12 comprise a plurality of turns of an electrical conductor spirally wound around a common axis. The lead 14 is attached to the outer turn 1A of the coil disk 10 to provide the initial connection to the portion of the winding 11 shown in FIG. 1. The numbers illustrated for each turn in FIG.

1 indicate the number of turns the conductor makes in progressing from the input lead 14. Thus, the conductor spirals inwardly from the position of turn 1A, to turn 2A, to turn 3A, etc. The turns which provide a single path across the radialbuild of a disk are referred to as a coil section. For example, the turns 1A, 2A, 3A and 4A form a coil section in the disk 10.

FIG. 2 is a diagram illustrating, in another form, the conductor development of the winding 11. The dashed lines 18, and 22 represent the connections between the coil disks 10 and 12 are not considered to have any substantial length compared to the length of the conductors of the disks. The disks illustrated in FIG. 2 show only one turn of each conductor in the disk for simplicity. Correspondence with FIGS. 1 and 2 can be achieved by aligning disk 10 over the top of disk 12 of FIG. 2, and by adding two additional turns to each disk in FIG. 2.

FIG. 2 can be used to help explain why it is believed the finish-finish connection arrangement shown in FIGS. 1 and 2 does not provide stress distributions as good as that provided by the winding configuration illustrated in FIGS. 3 and 4, which will be described in more detail hereinafter. Surge voltages, such as voltages caused by lightning strokes, contain highfrequency components. These components tend to produce current distributions along the winding conductors in much the same manner as current distributions along transmission lines, since the length of the winding conductors at the high frequencies involved is an appreciable amount of a wavelength at that frequency. In FIG. 2, the arrows indicate the direction of current flow in the winding 11 at the instant when the current 24 traveling into the disk 10 is at its greatest amplitude.

The resonant properties of the winding 11 cause the current distribution indicated by the direction of the currents 26 shown in FIG. 2. The current at the ends of the finish-finish connection 18 is directed opposite to the current entering and leaving the winding since it is located at the midpoint in the conductor path and is therefore l80 out-of-phase with the currents in the leads 12 and 14. This result is similar to the current distribution along a transmission line having a length equal to one wavelength of the current frequency. It is pointed out that the current changes phase by the amount of 180 for every two turns of the conductor.

The currents in the conductors forming the outer two turns of each coil disk provide flux therebetween which is directed out of the plane of the Figure. Since the coil disk 10 is physically positioned over the disk 12, the flux 30 is aligned with the flux 32. The mutual coupling between these turns is considerable due to the same direction of the the flux. It is this mutual coupling that is considered important in determining the surge voltage stress distribution on an interleaved winding.

When the mutual coupling is relatively low between cooil sections due to the aligned magnetic fluxes having opposite directions, as shown in FIG. 4, the stress distribution is enhanced. FIGS. 3 and 4 are diagrams of an interleaved winding constructed according to'U.S. Pat. No. 3,477,052. This type of winding exhibits improved stress characteristics to chopped wave and front-ofwave voltage surges, with the improvement believed to be caused by the lower mutual coupling between the coil sections. In FIG. 3, the winding includes the disk 34 which consists of two coil sections which are interleaved with each other. The disk 36 is similarly constructed. As illustrated in FIG. 4, the fluxes 37 established by the currents 39 along the conductors are directed in opposite directions. It is believed that the mutual coupling reduction provided thereby explains the better surge voltage performance of the winding 35 with respect to the winding 11.

FlG. 5 is a partial view illustrating a winding 40 constructed according to one embodiment of this invention. The winding 40 is disposed around the lowvoltage winding 42 which is positioned around the magnetic core 44. The winding 40 includes a plurality of electrical conductors spirally wound around a common axis 45 to form the coil disks 46, 48, and 52. The start'start connections 54 and 55 are of the transposing type which provides the most convenient mechanical form of interconnection between the coil disks. The finish-finish connections, such as connection 56, and arranged in a manner which, with the odd number of turns in every other coil disk, provides good electrical stress characteristics to applied voltage surges.

The lead 62 provides an input connection to the outer turn 1A. The letter designations are used to eliminate confusion between conductor turns and other reference numerals and to generally indicate which conductor used during the construction of the winding forms the particular turn. The conduction path progresses inwardly through the turns 1A, 2A, 3A and 4A, which form a first coil section in the coil disk 46. After traversing the start-start connection 55, the conduction path progresses outwardly through the turns 5A, 6A, 7A, 8A and 9A, which form a first coil section in the coil disk 48. The additional turn in the first coil section of the disk 48 is required to provide the desired current relationships for relatively low mutual coupling. After traversing the finish-finish connection 56, the conduction path progresses inwardly through turns 10B, 11B, 12B and 13B, which forms a second coil section in the coil disk 46. The conduction path is then transferred through the start-start connection 54 and progresses outwardly through the turns 14B, 15B, 16B and 17B, which form the second coil section in the coil disk 48. The finish-finish connection 58 interconnects the turn 17B with the turn 1A of the coil disk 50. Disks 50 and 52 are constructed similar to the disks 46 and 48.

The significance of this unique winding development may be indicated by the spiral diagram of the outer turns of winding 40, which is shown in FIG. 6. Intermediate turns of the disks 46 and 48 are not illustrated. Although the lowest resonant frequency of the winding 40 may be lower than that of the windings 11 and 35, the conductors of the winding 40 may be regarded as a transmission line with a total length between the leads 62 and 58 equal to one wavelength at this resonant frequency. Thus, with the direction of the currents 64 and 66 as indicated, the currents 68 and 70 are established along the conductor in the directions illustrated. This produces a magnetic flux 72 and a magnetic flux 74 which are directed in opposite directions. The low mutual coupling resulting therefrom improves the oscillatory characteristics of the winding 40 and enhances its stress distribution for chopped wave and front-of-wave voltage surges.

FIG. 7 illustrates another embodiment of the invention. Only two disks are illustrated for the winding 76, although more disks may be used without departing from the invention. The lead 78 provides an input connection to the turn 1A. The conduction path progresses inwardly through the turns 1A, 2A, 3A and 4A, which form the first coil section in the coil disk 80. The conduction path then traverses the start-start connection 84 and progresses outwardly through the turns 5A, 6A,

7A and 8A, which form the first coil section in the coil disk 82. After traversing the finish-finish connection 88, the conduction path progresses inwardly through the turns 9B, 108, 1 1B and 128, which form the second coil section in coil disk 80. The conduction path is then transferred through the start-start connection 86 and progresses outwardly through the turns 133, 148,158, 168 and 17 B, which form the second coil section in the coil disk 82, to the lead 90. The extra turn in the first coil section of the coil disk 82 is required to provide the desired current relationships for relatively low mutual coupling. Although the conduction path has been described as originating at the lead 78 and terminating at the lead 90, the path may be described as originating at the lead 90 and terminating at the lead 78 without changing the structure of the winding 76 or departing from the scope of the invention.

The current-turn relationship for the winding 76 is illustrated in FIG. 8. Assuming that the resonant frequency of the winding 76 is such that the length of the conductors forming the winding is equal to one wavelength at the resonant frequency, the currents in the leads 78 and 90 are in-phase with each other and travel in the same direction through the leads. The current relationships are illustrated for the instant of time when the currents at the leads are greatest since it is this condition which produces the most flux near the outer turns of the winding. The currents 92 and 94 are directed in the opposite direction with respect to the currents 96 and 98 since the currents along the conductors change direction when traveling more than ninety electrical degrees from the lead currents. In other words, the currents 96 and 98 are located at peaks on the sinewave-distributed current through the conductors, and the currents 92 and 94 are displaced more than ninety electrical degrees from these currents, hence they have a different direction.

The flux 100 produced between the outermost turns of the coil sections in the coil disk 80 is directed into the plane of the figure. The flux 102 produced between the outermost turns of the coil sections in the disk 82 is directed out of the plane of the figure. Hence, the flux 100 and the flux 102 are in opposite directions and the mutual coupling is relatively low.

FIG. 9 is a view of a winding 106 constructed according to another embodiment of this invention. A reduction in mutual coupling is provided by this arrangement in a manner similar to that of the windings 40 and 76; however, winding 106 has more than one conductor connected in parallel to form a unique configuration. The winding 106 would normally be wound using four conductors. The letter designations A, B, C and D identify these conductors.

The lead 112 provides an input to the turn 1C. The conduction path progresses inwardly through the turns 1C and 2C, which form the first coil section in the coil disk 108. The conduction path traverses the start-start connection 116 and progresses outwardly through the turns 3C and 4C, which form the first coil section in the coil disk 110. After traversing the finish-finish connection 118, the conduction path progresses inwardly through the second coil section in the coil disk 108, which consists of turns 5D, 6D and 7D. The conduction path is then transferred throught the startstart connection 120 and progresses outwardly through the second coil section in the disk 110, which consists of the turns 8D and 9D.

A'similar conduction path progession exists for the path beginning at the lead 114. Briefly, this path progresses inwardly through the third coil section in the disk 108, outwardly through the third coil section in the 5 disk 1 l0, inwardly through the fourth coil section in the disk 108, and outwardly through the fourth coil section in the disk 110 to the turn 9B. As previously stated, the progression of the conduction paths may be described by first entering one of the leads 122 or 124 and progressing to the lead 112 or 114.

FIG. is a spiral diagram of the winding 106 illustrated in FIG. 9. Each conduction path is arranged to provide minimum mutual coupling between its turns. For example, the current 130 enters the winding 106 in one conduction path of the disk 108 and is equal to the current 132 leaving the same conduction path in disk 110, assuming a transmission line type of distribution at a resonant frequency of the winding 106 with applied voltage surges. The currents 134 and 136 represent the currents in this conduction path at a specific location between the leads 114 and 122. The flux 138 provided by the currents 130 and 134 is directed in the opposite direction from the flux 140 which is provided by the currents 132 and 136. Thus, the mutual coupling between the same conduction path in adjacent disks is relatively low. A similar flux relationship exists for the conduction path between the leads 112 and 124. However, the direction of the flux in each disk is opposite to that shown in FIG. 10 when the current in the leads 112 and 124 is directed as indicated.

Each of the unique arrangements disclosed herein reduces the mutual coupling between the same conduction path in different coil disks. This is accomplished without a complicated interconnection arrangement. Thus, the advantages of both types of prior art interleaved windings are incorporated into a single winding in a new and useful manner.

Since numerous changes may be made in the abovedescribed apparatus, and since different embodiments of the invention may be made without departing from the spirit thereof, it is intended that all of the matter contained in the foregoing description, or shown in the accompanying drawing, shall be interpreted as illustrative rather than limiting.

I claim as my invention:

1. An interleaved winding for electrical inductive apparatus, comprising:

at least first and second coil disks disposed axially adjacent to each other, said first coil disk containing an even number of turns of an electrical conductor, and said second coil disk containing an odd number of turns of an electrical conductor;

start-start connections which connect together and radially transpose the conductors of the first and second coil disks; and,

a finish-finish connection which connects together the outermost turn of the second coil disk to the turn of the first coil disk which is adjacent to the outermost turn of the first coil disk.

2. An interleaved winding for electrical inductive apparatus, comprising:

at least first and second coil disks disposed axially adjacent to each other, said first coil disk containing an even number of turns of an electrical conductor, and said second coil disk containing an odd number of turns of an electrical conductor;

start-start connections which connect together and radially transpose the conductors of the first and second coil disks;

a finish-finish connection which connects together the outermost turn of the first coil disk to the second turn from the outermost turn of the second coil disk; and,

a finish-finish connection which connects together the outermost turn of the second coil disk to the second turn from the outermost turn of the first coil disk. 

1. An interleaved winding for electrical inductive apparatus, comprising: at least first and second coil disks disposed axially adjacent to each other, said first coil disk containing an even number of turns of an electrical conductor, and said second coil disk containing an odd number of turns of an electrical conductor; start-start connections which connect together and radially transpose the conductors of the first and second coil disks; and, a finish-finish connection which connects together the outermost turn of the second coil disk to the turn of the first coil disk which is adjacent to the outermost turn of the first coil disk.
 2. An interleaved winding for electrical inductive apparatus, comprising: at least first and second coil disks disposed axially adjacent to each other, said first coil disk containing an even number of turns of an electrical conductor, and said second coil disk containing an odd number of turns of an electrical conductor; start-start connections which connect together and radially transpose the conductors of the first and second coil disks; and, a finish-finish connection which connects together the outermost turn of the first coil disk to the turn of the second coil disk which is adjacent to the outermost turn of the second coil disk.
 3. An interleaved winding for electrical inductive apparatus, comprising: at least first and second coil disks disposed adjacent to each other, said first and second coil disks each containing an odd number of turns of an electrical conductor; start-start connections which connect together and radially transpose the conductors of the first and second coil disks; a finish-finish connection which connects together the outermost turn of the first coil disk to the second turn from the outermost turn of the second coil disk; and, a finish-finish connection which connects together the outermost turn of the second coil disk to the second turn from the outermost turn of the first coil disk. 